Great article from knowyourdslr.com about how to remove dust spots from your photos:
Spot Healing Tool
If you use a DSLR, sooner or later you’re going to find yourself swapping lenses – that kit lens that came with the camera isn’t going to do all the jobs all the time. That means, sooner or later, you’re going to find yourself facing a problem that photographers have faced since the advent of interchangeable lenses: dust.
Dust is a huge problem: it’s next to impossible to prevent, hard to get rid of and it ruins the best of shots. Many recent DSLRs have self-cleaning sensors to try to minimise the problem, and some can have custom dust maps created so that dust spots are removed in-camera, but knowing how to use the heal tool to get rid of those conspicuous dark spots is a must.
Williamo's Blog 
This article is a great tutorial on cleaning dusty pictures with photoshop. Changing lenses sure does risk your sensor, but it is unavoidable.
I am a fan of the photoshop option combined with shooting at low f-stops. I put more cleaning options and shots here:
http://blogs.adamparkerphotography.com/blog/Ive-got-sensor-dust-what-should-I-do/13/
Great job with your post, I’ll put a link over on my post, thanks.